Question 8 Using converse of basic proportionality theorem, prove that the line joining the mid-points of any two sides of a triangle is parallel to the third side.
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Solution
Given, ΔABC in which D and E are the mid points of AB and AC respectively such that AD=BD and AE=EC. To Prove that DE || BC Proof D is the mid-point of AB (Given) ∴AD=DB ⇒ADBD=1...(i) Also, E is the mid-point of AC (Given) ∴AE=EC ⇒AEEC=1.....(ii) From equation (i) and (ii), we get ADBD=AEEC, hence, DE || BC [By converse of Basic Proportionality Theorem]